﻿using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.Runtime.InteropServices;

// http://www.developerfusion.com/code/4630/capture-a-screen-shot/

namespace HelperTools.SystemTools
{
	/// <summary>
	/// Provides functions to capture the entire screen, or a particular window, and save it to a file.
	/// </summary>
	public class ScreenCapture
	{
		/// <summary>
		/// Creates an Image object containing a screen shot of the entire desktop
		/// </summary>
		/// <returns></returns>
		public Image CaptureScreen()
		{
			return CaptureWindow(User32.GetDesktopWindow());
		}
		/// <summary>
		/// Creates an Image object containing a screen shot of a specific window
		/// </summary>
		/// <param name="handle">The handle to the window. (In windows forms, this is obtained by the Handle property)</param>
		/// <returns></returns>
		public Image CaptureWindow(IntPtr handle)
		{
			// get te hDC of the target window
			IntPtr hdcSrc = User32.GetWindowDC(handle);
			// get the size
			User32.RECT windowRect = new User32.RECT();
			User32.GetWindowRect(handle, ref windowRect);
			int width = windowRect.right - windowRect.left;
			int height = windowRect.bottom - windowRect.top;
			// create a device context we can copy to
			IntPtr hdcDest = GDI32.CreateCompatibleDC(hdcSrc);
			// create a bitmap we can copy it to,
			// using GetDeviceCaps to get the width/height
			IntPtr hBitmap = GDI32.CreateCompatibleBitmap(hdcSrc, width, height);
			// select the bitmap object
			IntPtr hOld = GDI32.SelectObject(hdcDest, hBitmap);
			// bitblt over
			GDI32.BitBlt(hdcDest, 0, 0, width, height, hdcSrc, 0, 0, GDI32.SRCCOPY);
			// restore selection
			GDI32.SelectObject(hdcDest, hOld);
			// clean up
			GDI32.DeleteDC(hdcDest);
			User32.ReleaseDC(handle, hdcSrc);
			// get a .NET image object for it
			Image img = Image.FromHbitmap(hBitmap);
			// free up the Bitmap object
			GDI32.DeleteObject(hBitmap);
			return img;
		}
		/// <summary>
		/// Captures a screen shot of a specific window, and saves it to a file
		/// </summary>
		/// <param name="handle"></param>
		/// <param name="filename"></param>
		/// <param name="format"></param>
		public void CaptureWindowToFile(IntPtr handle, string filename, ImageFormat format)
		{
			Image img = CaptureWindow(handle);
			img.Save(filename, format);
		}
		/// <summary>
		/// Captures a screen shot of the entire desktop, and saves it to a file
		/// </summary>
		/// <param name="filename"></param>
		/// <param name="format"></param>
		public void CaptureScreenToFile(string filename, ImageFormat format)
		{
			Image img = CaptureScreen();
			img.Save(filename, format);
		}

		/// <summary>
		/// Helper class containing Gdi32 API functions
		/// </summary>
		private class GDI32
		{

			public const int SRCCOPY = 0x00CC0020; // BitBlt dwRop parameter
			[DllImport("gdi32.dll")]
			public static extern bool BitBlt(IntPtr hObject, int nXDest, int nYDest, int nWidth, int nHeight, IntPtr hObjectSource, int nXSrc, int nYSrc, int dwRop);
			[DllImport("gdi32.dll")]
			public static extern IntPtr CreateCompatibleBitmap(IntPtr hDC, int nWidth, int nHeight);
			[DllImport("gdi32.dll")]
			public static extern IntPtr CreateCompatibleDC(IntPtr hDC);
			[DllImport("gdi32.dll")]
			public static extern bool DeleteDC(IntPtr hDC);
			[DllImport("gdi32.dll")]
			public static extern bool DeleteObject(IntPtr hObject);
			[DllImport("gdi32.dll")]
			public static extern IntPtr SelectObject(IntPtr hDC, IntPtr hObject);
		}

		/// <summary>
		/// Helper class containing User32 API functions
		/// </summary>
		private class User32
		{
			[StructLayout(LayoutKind.Sequential)]
			public struct RECT
			{
				public int left;
				public int top;
				public int right;
				public int bottom;
			}
			[DllImport("user32.dll")]
			public static extern IntPtr GetDesktopWindow();
			[DllImport("user32.dll")]
			public static extern IntPtr GetWindowDC(IntPtr hWnd);
			[DllImport("user32.dll")]
			public static extern IntPtr ReleaseDC(IntPtr hWnd, IntPtr hDC);
			[DllImport("user32.dll")]
			public static extern IntPtr GetWindowRect(IntPtr hWnd, ref RECT rect);
		}
	}
}